Slug density‐seedling establishment relationships in a pasture renovated by direct drilling

Abstract

Ryegrass and white clover were sown singly or in combination at various seeding rates by direct drilling into plots in which a range of slug densities had been established by molluscicide baiting. For both ryegrass and white clover, weights of individual seedlings and numbers and yields of seedlings per metre of drill row were significantly affected by slug density, ryegrass seed rate, clover seed rate and interactions of these factors. Plant losses increased asymptomatically with slug density, indicating higher rates of seedling destruction per slug at low slug densities.

Gastropods alien to South Africa cause severe environmental harm in their global alien ranges across habitats

“…Our results do not support the general importance ascribed to gastropod fecundity for their impacts (Barker, ; De Kock & Wolmarans, ; Keller et al., ; Rumi et al., ). Rumi et al.…”

“…Our results do not support the general importance ascribed to gastropod fecundity for their impacts (Barker, 1991;De Kock & Wolmarans, 2008;Keller et al, 2007;Rumi et al, 2010 only reached a score of MN (Table 1). These conflicting results may be due to the context dependency of alien introductions.…”

Comparison of Conventional and Minimal Tillage for Low-Input Pasture Improvement

“…Fenner (39) observed that the vulnerability of seedlings to snail ( Helix aspersa Müller) predation decreased rapidly with time and increase in seedling size; therefore conditions that slow seedling growth are likely to increase snail predation and reduce seedling survival. Legumes appear to be particularly vulnerable to mollusk damage when sown with minimal tillage (74) and are likely to be preferentially grazed in mixed pastures (5). Fungicidal seed dressing can increase establishment and early season yield of resown grasses (60) but there is little evidence of a difference in establishment response to fungicide use between seeds sown into cultivated ground and those sown by minimal tillage.…”

“…Lewis (61) suggested that increased soil bulk density might reduce seedling growth rate and prolong the period of greatest risk for pathogen infection, and it could be inferred that reduced tillage would thus increase the risk of disease infection and reduce seedling establishment. The effectiveness of pesticide or fungicide in improving yield is variable, and depends on the extent of pest or disease challenge to the crop (5,54,97). Modification of planting dates to avoid periods of high pest population may be more effective than pesticide application in reducing the effects of predators (15,54,74).…”

“…Pest and disease problems at establishment. Predation by a range of insect (15,74,98) or mollusk (5,15,33,57,93,98) pests may result in less effective establishment and reduced yield of newly-sown forages. This damage may be more acute in crops sown by minimal tillage than with conventional cultivation (33,57,74,94), however, Ellis et al (36) noted that the incidence of damage by frit fly (Oscinella frit L.) was greater in conventional than in no-till seedings, and attributed this to a dilution of predator effect over both resident and establishing plants.…”